It's closing argument time in Iowa Republican debate

Tonight's presidential debate in Iowa -- the last such meeting before the first votes are cast in the GOP nominating race -- may be the best chance the candidates get to make a convincing closing argument to voters.

After the event, broadcast on the Fox News Channel starting at 9 p.m. EST, there will be just two full weeks of retail campaigning sandwiched around an expected Christmas cease-fire. But given how the race has been heavily influenced by the dozen televised forums, this may be the last real opportunity for a narrative-changing moment to take hold.

An average of public polling compiled by Real Clear Politics shows Newt Gingrich with about a 9 percentage point lead in Iowa over Mitt Romney. Bunched closely behind him are Ron Paul, Rick Perry, Michele Bachmann and even Rick Santorum, who is perhaps campaigning harder for Hawkeye State Republicans' support than anyone.

We saw a glimpse of the candidates' strategies in the Saturday night debate. Bachmann made a play for what's left of the Herman Cain support base, offering a "win, win, win" plan in place of the famous "9-9-9" blueprint.

Perry had what some thought was his strongest performance to date, having shifted from a message centered on Texas' economic muscle to one aimed squarely at Iowa's powerful social conservative electorate. Bonus points were given for the friendly, pricey wager he chose not to accept from Romney over a federal healthcare mandate.

Gingrich tried simply to withstand the expected attacks that the rotating cast of front-runners has had to face, and by and large succeeded. And it was Romney leading that charge, though he ultimately left the debate with the most to explain.

Tonight, Romney can be expected to continue a full-on assault on Gingrich that has only escalated since Saturday. Of late, he's arguing that Gingrich has been an unreliable conservative voice since leaving the House speakership. After long keeping his sights trained on President Obama, the former Massachusetts governor is playing for his party's right flank, even unveiling "Reaganites for Romney" earlier Thursday.

Gingrich has been vowing to stay positive.

"I have only one opponent -- that's Barack Obama," he told voters in Fort Dodge Thursday afternoon. "I'm going to run this campaign on a positive basis because I believe the people of Iowa are smart enough that they can see the difference between somebody who's trying to help the country and somebody who's simply running a negative campaign."

Gingrich did show no hesitation about punching back in the last debate, with one prepared line arguing that the only reason Romney was not a career politician was because he lost a Senate race to Ted Kennedy.

Even if he sticks to defending himself, he may have an ally in Paul, who some Iowa Republicans see as a real sleeper in the Jan. 3 contest. Paul especially hammered Gingrich over his role as a paid adviser for Freddie Mac.

"Newt, I think you probably got some of our taxpayer's money," he said.

Something of a wild card will be Jon Huntsman Jr.. He was absent from Saturday's debate but will be on stage this time. He's not competing in the Iowa caucuses but instead focusing his energy on the New Hampshire primary on Jan. 10. A new poll shows him in third place there, with 13%.